Reintroducing Cats?

I moved to my brothers, where he had 2 female cats. One was fixed and the other not. The cat that was not fixed had 3 kittens. He kept them all. So one of them I kept as my own. The 3 kittens and the mama cat and the other were all together. We all ended up having to move. My kitten is now 7 months old. His name is Sable.

Sable of course came with me to live. We have been in our home for about a week. I ended up going back to get the cat who was not fixed. Her name is Peaches. Keep in mind Peaches and Sable have lived together before. But when I brought Peaches home, Sable seems to act like he is mad. Why is that?

By CN from GA